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Integrated genomic analysis of chromosomal alterations and mutations in B-cell acute lymphoblastic leukemia reveals distinct genetic profiles at relapse

ABSTRACT: Background: The clonal basis of relapse in acute lymphoblastic leukemia (ALL) is complex and not fully understood. Methods: Next-generation sequencing (NGS), array comparative genomic hybridization (aCGH), and multiplex-ligation-dependent probe amplification (MLPA) were carried out in matched diagnosis-relapse samples from 13 B-cell precursor acute lymphoblastic leukemia (BCP-ALL) patients to identify patterns of genetic evolution that could account for the phenotypic changes associated with disease relapse. Findings: The integrative genomic analysis of aCGH, MLPA and NGS revealed that 100% of BCP-ALL patients showed at least one genetic alteration at diagnosis and relapse. In addition, there was a significant increase in the frequency of chromosomal lesions at the time of relapse (median, 6 alterations per sample) relative to that at diagnosis (median, 47 alterations) (p = 0.019). The combination of MLPA and aCGH techniques showed that IKZF1 was the most frequently deleted gene. Notably, TP53 was the most frequently mutated gene at relapse (31%). Two TP53 mutations were detected only at relapse, whereas the three others showed an increase of their mutational burden at relapse. Interpretation: Clonal evolution patterns were heterogeneous, involving acquisition, loss and maintenance of lesions at relapse. Therefore, this study confirmed that BCP-ALL is a genetically dynamic disease with distinct genetic profiles at diagnosis and relapse. The combination of the NGS, aCGH, and MLPA approaches enables better molecular characterization of the genetic profile in ALL patients during the evolution from diagnosis to relapse.

ORGANISM(S): Homo sapiens

PROVIDER: GSE128031 | GEO | 2020/08/12

REPOSITORIES: GEO

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Project description:Background: Retinoblastoma (RB) is the most common malignant childhood tumor of the eye and results from inactivation of both alleles of the RB1 gene. Nowadays RB genetic diagnosis requires classical chromosome investigations, Multiplex Ligation-dependent Probe Amplification analysis (MLPA) and Sanger sequencing. Nevertheless, these techniques show some limitations. We report our experience on a cohort of RB patients using a combined approach of Next-Generation Sequencing (NGS) and RB1 custom array-Comparative Genomic Hybridization (aCGH). Methods: A total of 65 patients with retinoblastoma were studied: 29 cases of bilateral RB and 36 cases of unilateral RB. All patients were previously tested with conventional cytogenetics and MLPA techniques. Fifty-three samples were then analysed using NGS. Eleven cases were analysed by RB1 custom aCGH. One last case was studied only by classic cytogenetics. Finally, it has been tested, in a lab sensitivity assay, the capability of NGS to detect artificial mosaicism series in previously recognized samples prepared at 3 different mosaicism frequencies: 10%, 5%, 1%. Results: Of the 29 cases of bilateral RB, 28 resulted positive (96.5%) to the genetic investigation: 22 point mutations and 6 genomic rearrangements (four intragenic and two macrodeletion). A novel germline intragenic duplication, from exon18 to exon 23, was identified in a proband with bilateral RB. Of the 36 available cases of unilateral RB, 8 patients resulted positive (22%) to the genetic investigation: 3 patients showed point mutations while 5 carried large deletion. Finally, we successfully validated, in a lab sensitivity assay, the capability of NGS to accurately measure level of artificial mosaicism down to 1%. Conclusions: NGS and RB1-custom aCGH have demonstrated to be an effective combined approach in order to optimize the overall diagnostic procedures of RB. Custom aCGH is able to accurately detect genomic rearrangements allowing the characterization of their extension. NGS is extremely accurate in detecting single nucleotide variants, relatively simple to perform, cost savings and efficient and has confirmed a high sensitivity and accuracy in identifying low levels of artificial mosaicisms.

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Integrated genomic analysis of chromosomal alterations and mutations in B-cell acute lymphoblastic leukemia reveals distinct genetic profiles at relapse

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